This invention relates generally to a dispensing pump of the pressure accumulating type, and more particularly to such a pump for dispensing product from a container having a low pressure gas therein for assisting in charging the pump chamber, the container being rechargeable with pressurized product outwardly of the plunger head.
Various dispensing devices for especially aerosols are capable of being refilled or recharged with pressurized product. These dispensing devices operate simply as control valves for expelling the pressurized product upon manual depression of a spray button, and the method of filling most widely used is known as pressure filling. The product to be dispensed is pressurized with a propellant liquid either of the type which vaporizes very rapidly when the product is at atmospheric pressure, or of the type in which the propulsion of the product is effected by maintaining the liquid composition in a container under the pressure of a permanent gas, such as nitrogen or carbon dioxide. The pressure filling technique is preferred over the alternative "cold-filling" method, and the use of a soluble or insoluble gaseous propellant, such as carbon dioxide, nitrous oxide or the like, for aerosol dispensers is much preferred and desirable over the use of liquid propellant gases such as propane and butane since the compressed gases are not incompatible with fragrances or sensitive drug products to be dispensed.
All of these aerosol dispensers are hermetically sealed to the container which offers many advantages over the known pump sprayers requiring the container to be vented to atmosphere. Thus, those products which cannot tolerate the presence of air which could result in the oxidation of the product, such as certain sensitive drugs, can be safely and effectively dispensed using one of the many types of aerosol dispensers on the market.
To satisfy a variety of needs, and as an alternative to the aforementioned valve control-type aerosol dispensers, a pump-type dispenser is disclosed in U.S. Pat. No. 3,211,346 which eliminates the need for venting the container since the material therein is under the pressure of an inert gas which ensures flow of the material into the pump chamber. However, this throttling-type pump suffers from the same disadvantages in use as any other pump of its class in that the discharge is slow to close upon the release of pressure on the finger actuator thereby causing unwanted dribbles and drips at the discharge, and air is introduced into the pump chamber as the pump volume expands upon release of finger pressure. Besides, no provision is made for charging or refilling the container with the dispenser in place.
A subsequent pump development is disclosed in FIGS. 6 and 7 of U.S. Pat. No. 4,271,875 in which a pressure build-up sprayer, also having no container vent, makes use of a compressed gas such as nitrogen for forcing product from the container up through the dip tube and into the pump chamber during the piston upstroke. Provision is made for filling this pump dispenser as pressurized fluids are injected from outside the pump chamber via a flexible gasket. However, such a pump structure possesses none of the advantages of my manual actuated dispensing pump, U.S. Pat. No. 4,050,613, on which the present application is based. For example, as pointed out in my earlier patent, the unitary plunger unit performs, in cooperation other components, the multiple functions of a pump cylinder, a piston for the pressure accumulation chamber, and a pressure actuated discharge valve. And, the unitary plunger of the aforementioned U.S. application Ser. No. 121,223 further performs the function of a container vent valve and, as set forth in the aforementioned related CIP application, the provision of a piston interfacing surface on the upper end of the plunger allows the plunger head to continue to expel product from the accumulation chamber after the end of the plunger downstroke. Furthermore, in that CIP application, the container vent valve can be disposed on the plunger head so as to provide a bearing member together with the retention bead on the cylindrical portion of the plunger head for resisting lateral and eccentric forces which may be applied to the plunger head so as to thereby isolate the plunger from the influence of those forces permitting it to respond without restraint in opening and closing the discharge. All these features of my prior and related developments have now been incorporated into an unvented dispenser of the pressure accumulating type which is adapted to be pressure filled.